The NIH Molecular Libraries and Imaging Roadmap Initiative will increase the availability of high throughput screening (HTS) to academic, government, and non-profit entities. We will develop an HTS assay for the identification of agonists and antagonists of the human trace amine associated receptor (hTAAR1). Until recently, it was postulated that the trace amines worked primarily through modulation of the activity of the classical biogenic amines. The recent identification of a class of receptors selective for the trace amines (Borowsky, Adham et al. 2001;Bunzow, Sonders et al. 2001) suggests that the trace amines also act as classical neurotransmitters. However, the physiological function of the trace amine receptors is not known. The identification of agonists and antagonists selective for this class of receptor will provide compounds useful as molecular probes of this function. We have generated stable cell lines expressing the human TAAR1 and propose to develop an HTS assay for the identification of small molecule compounds that act as agonists and antagonists of this receptor. The identification of these compounds will be greatly facilitated by the adaptation of trace amine receptor signaling to a readout which is amenable to HTS assays. hTAAR1 is a Gs linked receptor whose activation results in increased cAMP production. Although HTS assays for the evaluation of cAMP levels are available, we have chosen to develop an assay in which hTAAR1 is coupled to the Gq pathway and mobilization of intracellular calcium through association with the promiscuous Gq protein G116. This will result in a homogenous "mix-and-measure" cell based HTS assay for hTAAR1 activation for use in identifying small molecules that act as agonists or antagonists at the receptor. Borowsky, B., N. Adham, et al. (2001). "Trace amines: identification of a family of mammalian G protein- coupled receptors." Proceedings of the National Academy of Sciences of the United States of America. 98(16): 8966-8971. Bunzow, J. R., M. S. Sonders, et al. (2001). "Amphetamine, 3,4-methylenedioxymethamphetamine, lysergic acid diethylamide, and metabolites of the catecholamine neurotransmitters are agonists of a rat trace amine receptor." Molecular Pharmacology 60(6): 1181-1188. PUBLIC HEALTH RELEVANCE: Identification of small molecule compounds which modulate the activity of a newly identified trace amine associated receptor, hTAAR1, may provide selective small molecule agonists and antagonists for use as probes to elucidate the physiological role of this receptor. The identification of these compounds is hampered by the current technology used to measure hTAAR1 activity. This proposal will result in the development of new methods to measure receptor activity which will greatly facilitate the identification of potentially therapeutic compounds.